Cable-conveyed activation object

ABSTRACT

A technique that is usable with a well includes deploying a cable-conveyed object in a passageway of a string in the well; using the object to sense a property of an environment of the string and communicating an indication of the sensed property to an Earth surface of the well; remotely controlling an operation of the object to change a state of a first downhole valve assembly based at least in part on the communication; and using the object to control a state of the other downhole valve assembly(ies) during deployment of the object in the well.

BACKGROUND

For purposes of preparing a well for the production of oil or gas, at least one perforating gun may be deployed into the well via a conveyance mechanism, such as a wireline or a coiled tubing string. The shaped charges of the perforating gun(s) are fired when the gun(s) are appropriately positioned to perforate a casing of the well and form perforating tunnels into the surrounding formation. Additional operations may be performed in the well to increase the well's permeability, such as well stimulation operations and operations that involve hydraulic fracturing. The above-described perforating and stimulation operations may be performed in multiple stages of the well.

SUMMARY

The summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

In an example implementation, a technique that is usable with a well includes deploying a cable-conveyed object in a passageway of a string in the well; using the object to sense a property of an environment of the string and communicating an indication of the sensed property to an Earth surface of the well; remotely controlling an operation of the object to change a state of a first downhole valve assembly based at least in part on the communication; and using the object to control a state of at least one other downhole valve assembly during deployment of the object in the well.

In another example implementation, a technique that is usable with a well includes deploying a cable-conveyed object in a passageway of a string in the well; using the object to detect a location of the object and communicate an indication of the location to the Earth surface of the well; in response to the indication, remotely controlling operation of the object from the Earth surface to cause the object to engage a first valve assembly to change a state of the first valve assembly; and remotely controlling operation of the object from the Earth surface to cause the object to engage at least one additional valve assembly while the object is deployed in the well to change state(s) of the additional valve assembly(ies).

In yet another example implementation, an apparatus that is usable with a well includes a conveyance cable and an object that is adapted to be deployed in the well using the cable. The object includes a sensor to sense an environment of the object, a telemetry interface, an actuator, an expandable element and a control system. The control system uses the sensed environment to determine a location of the object; uses the telemetry interface to communicate an indication of the location uphole; uses the actuator to selectively expand the expandable element to engage a first valve assembly in response to receiving a first remotely communicated stimulus; uses the actuator to retract the expandable element in response to receiving a second remotely communicated stimulus; and uses the actuator to expand the expandable element to actuate a second valve assembly in response to receiving a third remotely communicated stimulus.

Advantages and other features will become apparent from the following drawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a multiple stage well according to an example implementation.

FIG. 2 is a schematic diagram of a cable-conveyed dart of FIG. 1 in a radially contracted state according to an example implementation.

FIGS. 3A, 3B and 3C are schematic diagrams illustrating use of the dart in a downhole stimulation operation according to an example implementation.

FIG. 4A is a flow diagram depicting a technique to use a cable-conveyed object in a well according to an example implementation.

FIG. 4B is a flow diagram depicting a technique to use a cable-conveyed activation object to perform a stimulation operation in a well according to an example implementation.

FIG. 5 is a schematic diagram of a dart illustrating a magnetic field sensor of the dart according to an example implementation.

FIG. 6A is a schematic diagram of a dart illustrating a differential pressure sensor of the dart according to an example implementation.

FIG. 6B is a flow diagram depicting a technique to determine the location of a cable-conveyed dart in a well based on a pressure sensed by the dart according to an example implementation.

FIG. 7 is a flow diagram depicting a technique to perform a multiple stage stimulation operation in a well using a cable-conveyed activation object according to an example implementation.

FIG. 8 is a schematic diagram of a dart illustrating an electromagnetic coupling sensor of the dart according to an example implementation.

FIG. 9 is an illustration of a signal generated by the sensor of FIG. 8 according to an example implementation.

FIG. 10 is a flow diagram depicting use of an electromagnetic coupling sensor to sense a position of a cable-conveyed activation object according to an example implementation.

FIG. 11 is a schematic diagram of a dart according to an example implementation.

DETAILED DESCRIPTION

In general, systems and techniques are disclosed herein for purposes of deploying a cable-conveyed activation object into a well; using the object to sense its location (its location relative to a downhole, targeted tool assembly to be activated by the object, for example); communicating the sensed location to the Earth surface of the well; and based on this communicated position, controlling the object from the Earth surface to perform one or more downhole operations. In this context, a “cable-conveyed object” refers to an object that travels at least some distance in a well passageway while being attached to a cable-based conveyance mechanism.

As specific examples, the cable-based conveyance mechanism may be a cable that contains one or more electrical communication lines (called an “electric line” or a “wireline”) or a cable that does not contain any electrical communication lines (called a “slickline); and the activation object may be a dart, a ball or a bar that is suspended from the conveyance cable as it is run into the well, retrieved from the well or in general, has its downhole location controlled by the conveyance cable. Moreover, in accordance with some implementations, downhole actions that are performed by the activation object (such as actions in which the object radially expands or contract) may be controlled by command stimuli that are communicated to the object via the cable. In accordance with some implementations, the movement of the activation object through a given well passageway may be aided by pumping (i.e., pushing to object using a fluid), although pumping may not be employed to move the object in the well, in accordance with other implementations.

As just a few examples, the downhole operation may be a stimulation operation (a fracturing operation or an acidizing operation, as examples); an operation that is performed by a downhole tool assembly (the operation of a downhole valve assembly, the operation of a single shot tool assembly, or the operation of a perforating gun assembly, as examples); an operation that involves the formation of a downhole obstruction; or an operation that diverts fluid (the diversion of fracturing fluid into a surrounding formation, for example). Moreover, in accordance with example implementations, a single deployed cable-conveyed activation object may be used to perform multiple downhole operations in multiple zones, or stages, of the well, as further disclosed herein.

In accordance with example implementations, the cable-conveyed activation object travels in a passageway (a tubing string passageway, for example) of the well, autonomously senses its position as it travels in the passageway, and employs uphole telemetry communication to communicate its sensed position to the Earth surface. Moreover, in accordance with example implementations, the cable-conveyed activation object is constructed to be remotely operated from the Earth surface initiate/further a given downhole operation.

As a more specific example, the cable-conveyed activation object may, in general, have two physical states: a radially contracted state (i.e., a state in which the object has a relatively smaller overall outer cross-sectional dimension) and a radially expanded state (i.e., a state in which the object has a relatively larger overall cross-sectional dimension). The cable-conveyed activation object is initially radially contracted (i.e., has a reduced overall diameter) when the object is deployed into the well at the Earth surface, and as the conveyance cable is extended to lower the object into the well, the object continuously or intermittently communicates indications of its location uphole to the Earth surface as the object travels downhole. Based on the object's location, actions may be taken at the Earth surface to remotely control the state of the object. For example, when the object reaches a predetermined, targeted location, one or more actions may be taken at the Earth surface to remotely instruct the object to radially expand.

The cable-conveyed object may actuate a downhole tool assembly, such as a valve assembly, in ways other than radially expanding the object to engage the assembly. For example, in accordance with further, example implementations, the object may form a magnetic coupling with the tool assembly; using a sliding pin and key arrangement between the object and the assembly; and so forth.

The increased diameter of the object due to its radial expansion may be used to effect any of a number of downhole actions, such as shifting a valve, forming a fluid obstruction, actuating a tool, a construction of these actions, and so forth. Moreover, because the object remains radially contracted before reaching the predetermined location, the object may pass through downhole restrictions (valve seats, for example) that may otherwise “catch” the object, thereby allowing the object to be used in, for example, multiple stage applications in which the object is used in conjunction with seats of the same size so that the radial expansion of the object is used to select which seat catches the object.

In accordance with example implementations, the cable-conveyed activation object is a downhole communication node of an uphole telemetry system to continuously or intermittently transmit indications of the object's location to the Earth surface. For example, in accordance with some implementations, the object may contain a transmitter (a radio frequency (RF) transmitter, for example) that is constructed to communicate an electrical signal to one of more electrical communication lines of a wireline for purposes of transmitting data uphole, which represents the absolute or relative location of the object. As a more specific example, the electrical signal may represent a packet of telemetry data. Other uphole telemetry techniques may be used, in accordance with further, example implementations. For example, the object may contain an acoustic transducer to communicate its position uphole using acoustic pulses that are communicated via fluid or communicated along a slickline. As another example, the object may a tension-based transducer that has arms to selectively contact a wellbore or tubing string wall for purposes of creating tension pulses in the conveyance cable, which represents telemetry data indicative of the object's position. As yet another example, the object may contain an electromagnetic (EM) wave transducer for uphole telemetry communication. Thus, many variations are contemplated, which are within the scope of the appended claims.

As disclosed herein, the cable-conveyed activation object may sense its position based on features of a string in which the object travels, markers, formation characteristics, and so forth, depending on the particular implementation. As a more specific example, for purposes of sensing its downhole location, the cable-based activation object may be constructed to, during its travel, sense specific points in the well, called “markers” herein. Moreover, as disclosed herein, the cable-based activation object may be constructed to detect the markers by sensing a property of the environment that surrounds the object (a physical property of the string in which the object is disposed or a formation, as examples). The markers may be dedicated tags or materials that are installed in the well for location sensing by the object or may be formed from features (sleeve valves, casing valves, casing collars, and so forth) of the well, which are primarily associated with downhole functions, other than location sensing. As another example, the markers may be incorporated into a material that is used in the construction of the well, such as, for example, microelectromechanical system (MEMS)-based sensors that are deployed in a cement slurry. Moreover, as disclosed herein, in accordance with example implementations, the cable-conveyed activation object may be constructed to sense its location in other and/or different ways that do not involve sensing a physical property of its environment, such as, for example, sensing a pressure for purposes of identifying valves or other downhole features that the object traverses and/or passes in the vicinity of during its travel.

In accordance with further example implementations, activation of the object may be based on the measurement of a length, such as measurement of a length between certain features of the tubing string 130.

Referring to FIG. 1, as a more specific example of the object and its well environment, in accordance with some implementations, a multiple stage well 90 includes a wellbore 120, which traverses one or more formations (hydrocarbon bearing formations, for example). As a more specific example, the wellbore 120 may be lined, or supported, by a tubing string 130, as depicted in FIG. 1. The tubing string 130 may be cemented to the wellbore 120 (such wellbores typically are referred to as “cased hole” wellbores); or the tubing string 130 may be secured to the formation by packers (such wellbores typically are referred to as “open hole” wellbores). In general, the wellbore 120 extends through one or multiple zones, or stages 170 (four stages 170-1, 170-2, 170-3 and 170-4, being depicted as examples in FIG. 1).

It is noted that although FIG. 1 depicts a laterally extending wellbore 120, the systems and techniques that are disclosed herein may likewise be applied to vertical wellbores, such as the example vertical wellbores that are illustrated in FIGS. 3A, 3B and 3C and discussed below. In accordance with example implementations, the well may contain multiple wellbores, which contain tubing strings that are similar to the illustrated tubing string 130. Moreover, depending on the particular implementation, the well may be an injection well or a production well. Thus, many variations are contemplated, which are within the scope of the appended claims.

In general, the downhole operations that are performed using the cable-conveyed activation object may be multiple stage operations that may be sequentially performed in the stages 170 in a particular direction (in a direction from a toe end 182 of the wellbore 120 to a heel end 180 of the wellbore 120 or vice versa, as examples) or may be performed in no particular direction or sequence, depending on the implementation.

Although not depicted in FIG. 1, fluid communication with the surrounding reservoir may be enhanced in one or more of the stages 170 through, for example, abrasive jetting operations, perforating operations, and so forth.

In accordance with example implementations, the well of FIG. 1 includes downhole tool assemblies 152 (tool assemblies 152-1, 152-2, 152-3, 152-4 and 152-5, being depicted in FIG. 1 as examples) that are located in the respective stages 170. The tool assembly 152 may be any of a variety of downhole tool assemblies, such as a valve assembly (a circulation valve assembly, a casing valve assembly, a sleeve valve assembly, and so forth), a seat assembly, a check valve assembly, a plug assembly, a perforation gun assembly, and so forth, depending on the particular implementation. Moreover, the tool assembly 152 may contain different tools (a mixture of a casing valve assembly, a plug assembly, a check valve assembly, and so forth, for example).

A given tool assembly 152 may be selectively actuated by deploying the cable-conveyed activation object through the central passageway of the tubing string 130 and activating the object so that the object enters a state that is used to actuate the tool assembly 152. As an example, the general cross-dimensional size of the object may be expanded to actuate a given tool assembly 152. For these example implementations, the cable-based activation object, when in its radially contracted state, passes relatively freely through the central passageway of the tubing string 130 (and thus, through tool assemblies of the string 130), and when in its radially expanded state, the object is configured to land in, or, be “caught” by, a selected one of the tool assemblies 152 or otherwise secured at a selected downhole location (in general), for purposes of performing a given downhole operation. For example, a given downhole tool assembly 152 may catch the cable-conveyed activation object in its radially expanded state and for purposes of forming a downhole fluid obstruction, or barrier in the tubing string 130. The tubing string 130 uphole of the fluid barrier may then be pressurized to actuate the tool assembly 152.

For the specific example of FIG. 1, the cable-conveyed activation object is a dart 100, which, as depicted in FIG. 1, may be deployed from the Earth surface E into the tubing string 130 at the end of a conveyance cable 101 and propagate along the central passageway of the string 130 as the dart 100 is lowered into the well by the cable 101. Based on the indications of the dart's position that are communicated by the dart 100 uphole, corresponding actions may be taken at the Earth surface E to control the dart's downhole state. For example, commands may be communicated downhole (via the cable 101, via acoustic signals, electromagnetic signals, conveyance line movement and so forth) for purposes of instructing the dart 100 to radially expand and engage the next tool assembly 152 that the dart 100 encounters.

In accordance with an example implementation, the dart 100 may sequentially engage the tool assemblies 152 of the stages 170-4, 170-3, 170-2 and 170-1 in that order. For this example, the dart 100 may be deployed on the cable 100 into the central passageway of the tubing string 130 from the Earth surface E, and the cable 100 is used to lower the dart 100 downhole. When the dart 100 is in proximity of the tool assembly 152 of the stage 170-4 (as indicated by the uphole telemetry information that is communication by the dart 100), an operator at the Earth surface E takes action to cause the dart 100 to radially expand so that the dart 100 engages a dart catching seat of the tool assembly 152-4. Using the resulting fluid obstruction, or barrier, that is created by the dart 100 landing in the tool assembly 152-4, fluid pressure may be applied uphole of the dart 100 (by pumping fluid into the tubing string 130, for example) for purposes of actuating the tool assembly 152-4.

The dart 100 is constructed to subsequently radially contract to release itself from the tool assembly 152-4 (as further disclosed herein), be pulled uphole via the cable 101, and be controlled to radially expand inside of the tool assembly 152-3 of the stage 170-3 to create another fluid barrier. Using this fluid barrier, the portion of the tubing string 130 uphole of the dart 100 may be pressurized for purposes of actuating the tool assembly 152-3. The above-described process may then be repeated for the tool assemblies 152 in stages 170-2 and 170-1.

Although examples are disclosed herein in which the dart 100 may be controlled to radially expand inside a tool assembly, in accordance with further example implementations, the dart 100 is constructed to secure itself to an arbitrary position of the string 130, which is not part of a tool assembly. Thus, many variations are contemplated, which are within the scope of the appended claims.

For the specific example of FIG. 1, the dart 100 senses its downhole location by sensing downhole markers 160. For example, as depicted in FIG. 1, each stage 170 may contain a marker 160, and each marker 160 may be embedded in a different tool assembly 152. The marker 160 may be a specific material, a specific downhole feature, a specific physical property, a radio frequency (RF) identification (RFID), tag, and so forth, depending on the particular implementation.

It is noted that each stage 170 may contain multiple markers 160; a given stage 170 may not contain any markers 160; the markers 160 may be deployed along the tubing string 130 at positions that do not coincide with given tool assemblies 152; the markers 160 may not be evenly/regularly distributed as depicted in FIG. 1; and so forth, depending on the particular implementation. Moreover, although FIG. 1 depicts the markers 160 as being deployed in the tool assemblies 152, the markers 160 may be deployed at defined distances with respect to the tool assemblies 152, depending on the particular implementation. For example, the markers 160 may be deployed between or at intermediate positions between respective tool assemblies 152, in accordance with further implementations. Thus, many variations are contemplated, which are within the scope of the appended claims.

In accordance with an example implementation, a given marker 160 may be a magnetic material-based marker, which may be formed, for example, by a ferromagnetic material that is embedded in or attached to the tubing string 130, embedded in or attached to a given tool housing, and so forth. By sensing the markers 160, the dart 100 may determine its absolute or relatively downhole location and use uphole telemetry to communicate that position to the Earth surface E. In this manner, the dart 100 may count the markers 160, determine its location based on the count and communicate, via uphole telemetry, the location to the Earth surface E. In further implementations, the dart 100 may sense the markers 160 and transmit an indication of a sensed marker 160 uphole to the Earth surface E every time a marker 160 is sensed, so that a human or electronics at the Earth surface E may count the markers to determine the dart's location.

The dart 100 may, in accordance with example implementations, detect specific markers 160, while ignoring other markers 160. In this manner, another dart may be subsequently deployed into the tubing string 130 to count the previously-ignored markers 160 (or count all of the markers, including the ignored markers, as another example) in a subsequent operation, such as a remedial action operation, a fracturing operation, and so forth. In this manner, using such an approach, specific portions of the well may be selectively treated at different times. In accordance with some example implementations, the tubing string 130 may have more tool assemblies 152 (see FIG. 1), such as sleeve valve assemblies (as an example), than are needed for current downhole operations, for purposes of allowing future refracturing or remedial operations to be performed.

As a more specific example, the dart 100 may be deployed on the cable 101 for purposes of performing a being caught in the tool assembly 152-4, which, for this example, has there tool assemblies 152-1, 152-2 and 153 that are location uphole of the assembly 152-4. Therefore, after the dart 100 has passed by three markers 160 (i.e., the markers 160 of the tool assemblies 152-1, 152-2 and 152-3), the Earth surface E has received an indication that the dart 100 is between the tool assemblies 152-3 and 152-4. At this point, the dart 100 may be remotely controlled from the Earth surface to cause the dart 100 to radially expand so that when the cable 101 further lowers the dart 100 downhole, the dart 100 engages the tool assembly 152-4.

Referring to FIG. 2, in accordance with an example implementation, the dart 100 has one or multiple, outer elastomer rings 252, which are constructed to radially expand (be compressed between opposing pistons, or thimbles 254 and 256, for example) for purposes of radially expanding the dart 100 to lodge the dart 100 inside a given sleeve valve assembly. In this manner, when deployed into the well, in accordance with example implementations, the thimbles 254 and 256 are spaced apart to allow the elastomer element(s) 252 to relax to reduce the outer diameter of the dart 100 to a sufficiently small diameter to allow the dart 100 to pass through other passageways, valve assemblies, and so forth.

As depicted in FIG. 2, in accordance with an example implementation, the dart 100 includes a controller 224 (a microcontroller, microprocessor, field programmable gate array (FPGA), or central processing unit (CPU), as examples), which is constructed to communicate with a telemetry interface 250 of the dart 100 for purposes of communicating sensed dart positions to the Earth surface E, receive data indicative of commands for the dart 100 (commands to radially expand and retract, as examples), and so forth. In accordance with example implementations, the controller 224 may include a memory (a volatile or a non-volatile memory, depending on the implementation) that stores program instructions and data for the controller 224.

In accordance with example implementations, the telemetry interface 250 may include a transceiver (RF transceiver, acoustic transceiver, and so forth) for purposes of communicating data to (uphole telemetry) the Earth surface and for purposes of communicating data and commands from (downhole telemetry) from the Earth surface. The uphole and/or downhole telemetry may involve the use of the cable 101, in accordance with example implementations. For example, the uphole/downhole telemetry may use one or more wires, fibers, and so forth of the cable 101. Moreover, in accordance with some example implementations, the telemetry interface 250 may control arms (not shown) that selectively contact the wellbore or tubing string wall for purposes of communicating data with the Earth surface via tension pulses. The telemetry interface 250 may also use, in accordance with further example implementations, acoustic signals, electromagnetic (EM) signals, acoustic pulses, fluid pulses, and so forth for uphole and/or downhole communications, depending on the particular implementation. Thus, the telemetry interface 250 may, for example, communicate stimuli uphole to indicate the dart's downhole position; and the telemetry interface 250 may receive stimuli communicated downhole for such purposes as directing the dart 100 to operate in a manner to engage a downhole tool assembly (such as a valve assembly), disengage from a given downhole tool assembly to allow the dart 100 to travel to other downhole positions, engage another downhole tool assembly, and so forth.

FIG. 2 also depicts an actuator 220 that is coupled to the controller 224 for purposes of controlling the radial expansion and contraction of the dart 100. In this regard, in accordance with some example implementations, the controller 224 controls the actuator 220 for purposes of compressing the thimbles 254 and 256 for purposes of radially expanding the resilient element 252 as well as radially expanding one or multiple slips 260 of the dart 100. In this regard, engagement of the slips 260 with a tubing string wall, sleeve valve, and so forth, stops downhole progress of the dart 100 and anchors the dart 100 to the surrounding member.

Among its other components, the dart 100 may have a downhole energy source, in accordance with further example implementations, such as a battery or a fuel cell, and in accordance with further example implementations, the dart 100 may receive its power from the cable 101 (for the case of a wireline, for example). Moreover, as shown in FIG. 2, in accordance with example implementations, the dart 100 may have a wiper 264 at its lower end for purposes of allowing the pumping of fluid to facilitate the movement of the dart 100 through the well. In further implementations, the dart may have power regulation circuitry that receives power either from the cable 100 or a downhole energy source and distributes regulated supply voltages to the electrical power consuming components of the dart 100.

As also depicted in FIG. 2, in accordance with example implementations, the dart 100 includes at least one sensor 230. In general, the sensor 230 may be used to detect markers 160 as well as detect other downhole features for purposes of acquiring an indication of the dart's downhole position, as further disclosed herein.

In accordance with example implementations, the sensor 230 provides one or more signals that indicate a physical property of the dart's environment (a magnetic permeability of the tubing string 130, a radioactivity emission of the surrounding formation, and so forth); the controller 224 use the signal(s) to determine a location of the dart 100; and the controller 224 correspondingly uses the telemetry interface 250 to communicate with the Earth surface E for purposes of informing an operator or circuitry at the Earth surface E as to the dart's location.

In accordance with example implementations, the sensor 230 senses a magnetic field. In this manner, the tubing string 130 may contain embedded magnets, and sensor 230 may be an active or passive magnetic field sensor that provides one or more signals, which the controller 224 interprets to detect the magnets. However, in accordance with further implementations, the sensor 230 may sense an electromagnetic coupling path for purposes of allowing the dart 100 to electromagnetic coupling changes due to changing geometrical features of the string 130 (thicker metallic sections due to tools versus thinner metallic sections for regions of the string 130 where tools are not located, for example) that are not attributable to magnets. In other example implementations, the sensor 230 may be a gamma ray sensor that senses a radioactivity. Moreover, the sensed radioactivity may be the radioactivity of the surrounding formation. In this manner, a gamma ray log may be used to program a corresponding location radioactivity-based map into a memory of the dart 100.

FIGS. 3A, 3B and 3C depicts deployment and use of the dart 100 in a multiple stage fracturing operation in a vertical wellbore that contains sleeve valve assemblies 300 and markers 160. For this example, the dart 100 is used to perform a fracturing operation in stage 170-3; and as shown in FIG. 3A, initially all of the sleeve valve assemblies 300 are closed so that radial fluid communication with the surrounding formations is prevented. The dart 100 is deployed into the tubing string 130 on the cable 101 and passes through valve assemblies 170-1 and 170-2. For this example implementation, the valve assembly 300 in the stage 170-3 contains a marker 160 that identifies the valve assembly 170-3 as being the valve assembly 300 that is targeted by the dart 100.

Referring to FIG. 3B, the dart's proximity to the stage 170-3 (and its associated marker 160) is detected at the Earth surface using the uphole telemetry communication from the dart 100. At this point, the dart 100 is remotely controlled from the Earth surface E to cause the dart 100 to radially expand above the valve assembly 300 of the stage 170-3 so that as the dart 100 is further deployed downhole, the dart 100 lodges in an inner sleeve 304 of the valve assembly 300, in shown in FIG. 3B. The lodging of the dart 100 in the inner sleeve 300 creates a fluid barrier in the tubing string 130. Referring to FIG. 3C, therefore upon application of hydraulic pressure above the barrier (by pumping fluid downhole into the central passageway of the tubing string 130), a downward shifting force is developed to shift the inner sleeve 304 downwardly to open radial fluid communication through the valve assembly's radial ports 302. At this point, fracturing fluid may be pumped downhole in the tubing string 130, and the fluid is diverted by the fluid barrier through the radial ports 302 and into the surrounding formation.

Continuing the example, the dart 100 may then be remotely controlled from the Earth surface to cause the dart 100 to radially contract at the conclusion of the fracturing of the zone associated with the stage 170-3. Once radially contracted, as an example, the cable 101 may be used to move the dart 100 uphole of the valve assembly 300 for the stage 170-2. For example, in accordance with some implementations, the cable 101 may be retracted to cause the dart 100 to pass through a marker (not shown) associated with the valve assembly 300 for the stage 170-2. Upon receiving an indication of this position of the dart 100, a command may then be communicated downhole to once again cause the dart 100 to radially expand. Next, the dart 100 may be lowered downhole to thereafter engage the inner sleeve 304 of the valve assembly for the stage 170-2. At this point, the radially expanded dart 100, now engaged with the inner sleeve 304, may be forced farther downhole using hydraulic pressure to shift the valve assembly 300 open. Once again, fluid may then be communicated using the fluid barrier created by the dart 100 and the open state of the valve assembly 300 for purposes of fracturing the associated zone. Other zones may be fractured using the above-described process.

Although the above-described multiple stage operation occurs in an uphole direction, it is understood that the dart 100 may be used for purposes of performing multiple stage operations in a downhole direction, in accordance with further, example implementations. For these implementations, the dart 100 may, while in the radially expanded state, be pulled uphole to subsequently reclose the valve assembly 300 before the dart 100 is radially contracted to allow the dart 100 to move to the next valve assembly 300.

Thus, in general, a technique 400 that is depicted in FIG. 4A includes deploying (block 402) a cable-conveyed object in a passageway of a string in a well and using (block 404) the object to sense a property of an environment of the string and communicate an indication of the sensed property to the Earth surface of the well. Pursuant to the technique 400, the object may be remotely controlled (block 406) based on the communicated indication to engage a downhole valve assembly and transition the assembly from one state (a closed state, for example) to another state (an open state, for example). The object may then be used to perform (block 408) a downhole operation.

For example, in accordance with some implementations, the object may be radially expanded to engage a sleeve of a valve assembly and shift the sleeve to open the valve assembly. Due to the fluid barrier, or obstruction, that is created by the now lodged object, fluid may be diverted into the surrounding formation through radial ports of the opened valve assembly to conduct a downhole operation, such as a stimulation operation (a fracturing operation, as a more specific example). The technique 400 further includes allowing (block 410) the object to travel to the next downhole valve assembly and repeating blocks 404, 406 and 408 at least one additional time. In this regard, the object may be released by radially contracting the object (or by operating another type of release mechanism of the object) to allow the object to move to change the state of another downhole valve assembly and perform another stimulation operation in a similar manner.

A technique 420 that is depicted in FIG. 4B may be used for purposes of performing a stimulation operation in a well. Referring to FIG. 4B, pursuant to the technique 420, in a well, a cable-conveyed object is deployed in a passageway of a string, pursuant to block 422. The object is used (block 424) to sense a downhole location of the object and communicate an indication of the sensed location of the Earth surface of the well, pursuant to block 424. In response to this indication, operation of the object may be remotely controlled from the Earth surface to cause the object to radially expand in a given valve assembly, pursuant to block 426. A fluid barrier that is created by the radial expansion of the object is then used (block 426) to hydraulically shift the given valve assembly open so that a stimulation operation may be performed (block 430) in the zone that is associated with the given valve assembly.

Referring to FIG. 5 in conjunction with FIG. 2, in accordance with an example implementation, the sensor 230 of the dart 100 may include a coil 504 for purposes of sensing a magnetic field. In this manner, the coil 504 may be formed from an electrical conductor that has multiple windings about a central opening. When the dart passes in proximity to a ferromagnetic material 520, such as a magnetic marker 160 that contains the material 520, magnetic flux lines 510 of the material 520 pass through the coil 504. Thus, the magnetic field that is sensed by the coil 504 changes in strength due to the motion of the dart 100 (i.e., the influence of the material 520 on the sensed magnetic field changes as the dart 100 approaches the material 520, coincides in location with the material 520 and then moves past the material 520). The changing magnetic field, in turn, induces a current in the coil 504. The controller 224 (see FIG. 2) may therefore monitor the voltage across the coil 504 and/or the current in the coil 504 for purposes of detecting a given marker 160; and thereafter, the controller 224 may use the telemetry interface 250 for purposes of communicating to the Earth surface a detected position of the dart 100. The coil 504 may or may not be pre-energized with a current (i.e., the coil 504 may passively or actively sense the magnetic field), depending on the particular implementation.

It is noted that FIGS. 2 and 5 depict a simplified view of the sensor 230 and controller 224, as the skilled artisan would appreciate that numerous other components may be used, such as an analog-to-digital converter (ADC) to convert an analog signal from the coil 504 into a corresponding digital value, an analog amplifier, and so forth, depending on the particular implementation.

In accordance with example implementations, the dart 100 may sense a pressure to detect features of the tubing string 130 for purposes of determining the location/downhole position of the dart 100. For example, referring to FIG. 6A, in accordance with example implementations, the dart 100 includes a differential pressure sensor 620 that senses a pressure in a passageway 610 that is in communication with a region 660 uphole from the dart 100 and a passageway 614 that is in communication with a region 670 downhole of the dart 100. Due to this arrangement, the partial fluid seal/obstruction that is introduced by the dart 100 in its radially contracted state creates a pressure difference between the upstream and downstream ends of the dart 100 when the dart 100 passes through a valve assembly.

For example, as shown in FIG. 6A, a given valve may contain radial ports 604. Therefore, for this example, the differential pressure sensor 620 may sense a pressure difference as the dart 100 travels due to a lower pressure below the dart 100 as compared to above the dart 100 due to a difference in pressure between the hydrostatic fluid above the dart 100 and the reduced pressure (due to the ports 604) below the dart 100. As depicted in FIG. 6A, the differential pressure sensor 620 may contain terminals 624 that, for example, electrically indicate the sensed differential pressure (provide a voltage representing the sensed pressure, for example), which may be communicated to the controller 224 (see FIG. 2). For these example implementations, valves of the tubing string 130 are effectively used as markers for purposes of allowing the dart 100 to sense its position along the tubing string 130.

Therefore, in accordance with example implementations, a technique 680 that is depicted in FIG. 6B may be used in conjunction with the dart 100. Pursuant to the technique 680, cable-conveyed object is deployed (block 682) in a passageway of a string; and the object is used (block 684) to sense pressure as the object travels in a passageway of the string. The technique 680 includes selectively communicating (block 686) with the Earth surface to indicate detection of a valve assembly based at least in part on the sensed pressure.

In accordance with some implementations, the dart 100 may sense multiple indicators of its position as the dart 100 travels in the tubing string 130. For example, in accordance with example implementations, the dart 100 may sense both a physical property and another downhole position indicator, such as a pressure (or another property), for purposes of determining its downhole position. Moreover, in accordance with some implementations, the markers 160 (see FIG. 1) may have alternating polarities, which may be another position indicator that the dart 100 uses to assess/corroborate its downhole position. In this regard, magnetic-based markers 160, in accordance with an example implementation, may be distributed and oriented in a fashion such that the polarities of adjacent magnets alternate. Thus, for example, one marker 160 may have its north pole uphole from its south pole, whereas the next marker 160 may have its south pole uphole from its north pole; and the next the marker 160 may have its north pole uphole from its south pole; and so forth. The dart 100 may use the knowledge of the alternating polarities as feedback to verify/assess its downhole position.

Thus, referring to FIG. 7, in accordance with an example implementation, a technique 700 for autonomously operating an untethered object in a well, such as the dart 100, includes determining (decision block 704) whether a marker has been detected. If so, the dart 100 updates a detected marker count and updates its location and transmits an indication of its location uphole to the Earth surface, pursuant to block 708. The dart 100 further determines (block 712) its location based on a sensed marker polarity pattern, and the dart 100 may determine (block 716) its location based on one or more other measures (a sensed pressure, for example). If the dart 100 determines (decision block 720) that the marker count is inconsistent with the other determined locations, then the dart 100 adjusts (block 724) the marker count/location.

In accordance with example implementations, the dart 100 continually performs the above-described loop (sensing and transmitting its location uphole); and the radial expansion and contraction of the dart 100 are independently controlled. In further example implementations, when the dart 100 determines (decision block 728) that the dart 100 has received a command to expand, the dart 100 suspends the location transmission and performs functions related to expanding and contracting, as controlled from the Earth surface. In this manner, in accordance with example implementations, the dart 100 actuates (block 733) its actuator to cause the radial expansion of the dart 100 and thereafter waits (decision block 736) for a command to release the dart 100. In this regard, in accordance with example implementations, upon receiving a command to be released, the dart activates (block 740) a self-release mechanism to release the dart. For example, in accordance with some implementations, the dart 100 actuates the actuator in the opposite direction used to expand the dart for purposes of radially contracting the dart to allow the dart to be moved to the next valve assembly, be moved to another position in the well, and so forth. In accordance with example implementations, if the dart is to be radially expanded again (decision block 744), then control returns to decision block 704.

Other variations are contemplated, which are within the scope of the appended claims. For example, FIG. 8 depicts a dart 800 according to a further example implementation. In general, the dart 800 includes an electromagnetic coupling sensor that is formed from two receiver coils 814 and 816, and a transmitter coil 810 that resides between the receiver coils 815 and 816. As shown in FIG. 8, the receiver coils 814 and 816 have respective magnetic moments 815 and 817, respectively, which are opposite in direction. It is noted that the moments 815 and 817 that are depicted in FIG. 8 may be reversed, in accordance with further implementations. As also shown in FIG. 8, the transmitter 810 has an associated magnetic moment 811, which is pointed upwardly in FIG. 8, but may be pointed downwardly, in accordance with further implementations.

In general, the electromagnetic coupling sensor of the dart 800 senses geometric changes in a tubing string 804 in which the dart 800 travels. More specifically, in accordance with some implementations, the controller (not shown in FIG. 8) of the dart 800 algebraically adds, or combines, the signals from the two receiver coils 814 and 816, such that when both receiver coils 814 and 816 have the same effective electromagnetic coupling the signals are the same, thereby resulting in a net zero voltage signal. However, when the electromagnetic coupling sensor passes by a geometrically varying feature of the tubing string 804 (a geometric discontinuity or a geometric dimension change, such as a wall thickness change, for example), the signals provided by the two receiver coils 814 and 816 differ. This difference, in turn, produces a non-zero voltage signal, thereby indicating to the controller that a geometric feature change of the tubing string 804 has been detected.

Such geometric variations may be used, in accordance with example implementations, for purposes of detecting certain geometric features of the tubing string 804, such as, for example, sleeves or sleeve valves of the tubing string 804. Thus, by detecting and possibly counting sleeves (or other tools or features), the dart 800 may determine its downhole position and actuate its deployment mechanism accordingly.

Referring to FIG. 9 in conjunction with FIG. 8, as a more specific example, an example signal is depicted in FIG. 9 illustrating a signature 902 of the combined signal (called the “V_(DIFF)” signal in FIG. 9) when the electromagnetic coupling sensor passes in proximity to an illustrated geometric feature 820, such as an annular notch for this example.

Thus, referring to FIG. 10, in accordance with example implementations, a technique 1000 includes deploying (block 1002) a cable-conveyed object in a string and using (block 1004) the object to sense an electromagnetic coupling as the object travels in a passageway of the string. The technique 1000 includes selectively communicating (block 1006) with the Earth surface to indicate detection of a valve assembly based at least in part on the sensed electromagnetic coupling.

Thus, in general, implementations are disclosed herein for purposes of deploying a cable-conveyed object through a passageway of the string in a well and using the object to sense a location indicator as the object traverses the passageway. The object communicates an indication of its position to the Earth surface and is constructed to be remotely actuated from the Earth surface to selectively expand and retract. As disclosed above, the property may be a physical property such as a magnetic marker, an electromagnetic coupling, a geometric discontinuity, a pressure or a radioactive source. In further implementations, the physical property may be a chemical property or may be an acoustic wave. Moreover, in accordance with some implementations, the physical property may be a conductivity. In yet further implementations, a given position indicator may be formed from an intentionally-placed marker, a response marker, a radioactive source, magnet, microelectromechanical system (MEMS), a pressure, and so forth. The cable-conveyed activation object has the appropriate sensor(s) to detect the locations indicator(s), as can be appreciated by the skilled artisan in view of the disclosure contained herein.

Other implementations are contemplated and are within the scope of the appended claims. For example, in accordance with further example implementations, the dart may have a container that contains a chemical (a tracer, for example) that is carried into the fractures with the fracturing fluid. In this manner, when the dart is deployed into the well, the chemical is confined to the container. The dart may contain a rupture disc (as an example), or other such device, which is sensitive to the tubing string pressure such that the disc ruptures at fracturing pressures to allow the chemical to leave the container and be transported into the fractures. The use of the chemical in this manner allows the recovery of information during flowback regarding fracture efficiency, fracture locations, and so forth.

As another example of a further implementation, the telemetry interface 250 (see FIG. 2) of the dart 100 may be used for purposes of communicating information other than the above-described commands and locations. For example, in accordance with further example implementations, the telemetry interface 250 may be used by the controller 224 (see FIG. 2) for purposes of communicating a status of the dart to the Earth surface. For example, the status may be an acknowledgment that the dart 100 has expanded, contracted, and so forth. As another example, the status may be a status indicating whether dart 100 is functioning properly. Other information may be communicated using the telemetry interface 250, such as sensed downhole pressures, temperatures and so forth.

As yet another example, in accordance with some implementations, the cable-conveyed object may contain or be attached to a perforating gun assembly. In this regard, FIG. 11 depicts a cable-conveyed object 1100 in accordance with a further example implementation. For this example, the object 1100 includes a perforating gun assembly 1102. As an example, a firing head of the perforating gun assembly 1102 may be instructed to fire perforating charges (shaped charges, for example) of the assembly 1102 by remotely communicating stimuli to the assembly 1102 from equipment at the Earth surface of the well. For example, after the cable-conveyed object 1100 forms a fluid obstruction, pressure pulses may be communicated to the firing head using the fluid column above the object 1100. In further example implementations, the cable 101 may be moved in a predetermined pattern to send a firing command to the perforating gun assembly 1102. In yet further example implementations, pressure in the fluid column above the object 1100 (due to the object 1100 creating a fluid obstruction) may be used to cause the firing head to fire the perforating charges. Other stimuli (acoustic, electromagnetic (EM), electrical, and so forth) may be used to communicate with the firing head and with the object 1100 in general, in accordance with further example implementations.

Thus, in accordance with example implementations, the cable-conveyed object 1100 may be used to perforate a given zone, or stage of a well and then perform a stimulation operation in the stage before moving onto to the next stage where another set of stimulation and perforation operations are performed. Thus, the perforation and stimulation may be repeated for multiple zones. In further example implementations, the perforating gun assembly 1102 may be replaced with another type of perforating tool, such as an abrasive fluid-based jetting tool, for example.

While a limited number of examples have been disclosed herein, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations. 

What is claimed is:
 1. A method usable with a well, comprising: deploying a cable-conveyed object in a passageway of a string in the well; using the object to sense a property of an environment of the string and communicating an indication of the sensed property to an Earth surface of the well; remotely controlling an operation of the object to change a state of a first downhole valve assembly based at least in part on the communication; and using the object to control a state of at least one other downhole valve assembly during deployment of the object in the well.
 2. The method of claim 1, wherein the property comprises a physical property.
 3. The method of claim 2, wherein the physical property comprises a magnetic field produced by a magnetic marker, a geometric discontinuity of the string, an acoustic wave, a pressure or a conductivity.
 4. The method of claim 2, wherein the physical property comprises an element selected from the group consisting essentially of a dedicated marker, a radioactive source, a magnetic, a microelectromechanical system (MEMS)-based marker and a pressure.
 5. The method of claim 1, wherein deploying the cable-conveyed object comprises deploying the object on a wireline or a slickline.
 6. The method of claim 1, further comprising using the first downhole valve assembly to perform a stimulation operation.
 7. The method of claim 1, wherein remotely controlling the cable-conveyed object comprises transitioning the object between a radially contracted state and a radially expanded state.
 8. The method of claim 1, wherein using the object sense the property comprises sensing a repeating pattern along the string or sensing a feature of the well primarily associated with a function other than identifying a downhole location.
 9. The method of claim 1, wherein using the cable-conveyed object to sense the property comprises sensing a dedicated location identification marker, sensing a current in a coil of the object or sensing a magnetic field.
 10. The method of claim 1, wherein remotely controlling the cable-conveyed object further comprises forming a downhole obstruction inside the passageway of the string.
 11. The method of claim 1, wherein communicating the indication comprises communicating with the Earth surface using tension-based, acoustic-based, electrical signal-based, or electromagnetic wave-based telemetry.
 12. The method of claim 1, further comprising: perforating a segment of the well; using the first downhole valve assembly to fracture the segment of the well; perforating at least one other segment of the well; and using a fluid obstruction formed by the at least one other downhole valve assembly to fracture the at least one other segment of the well.
 13. The method of claim 12, wherein perforating the first segment and perforating the at least one other segment comprises using a perforating gun disposed on the object.
 14. A method usable with a well, comprising: deploying a cable-conveyed object in a passageway of a string in the well; using the object to detect a location of the object and communicate an indication of the location to the Earth surface of the well; in response to the indication, remotely controlling operation of the object from the Earth surface to cause the object to engage a first valve assembly to change a state of the first valve assembly; and remotely controlling operation of the object from the Earth surface to cause the object to engage at least one additional valve assembly while the object is deployed in the well to change a state of the at least one additional valve assembly.
 15. The method of claim 14, wherein remotely controlling operation of the object from the Earth surface comprises remotely controlling the object to cause the object to radially expand to engage a sleeve of the valve assembly.
 16. The method of claim 14, wherein remotely controlling the object comprises remotely controlling the object to form a fluid barrier in the string.
 17. The method of claim 14, wherein remotely controlling the object comprises remotely controlling the object to shift the valve assembly between open and closed states.
 18. The method of claim 14, wherein remotely controlling the valve comprises radially expanding the valve to lodge the valve in a sleeve of the valve assembly and create a fluid barrier, the method further comprising: using the fluid barrier to pressurize the string to hydraulically shift the sleeve to cause the valve assembly to transition from a first state to a second state; and using the fluid barrier to divert fluid to perform a stimulation operation in a stage associated with the valve assembly with the valve assembly in the second state.
 19. The method of claim 18, further comprising: remotely controlling the object from the Earth surface to cause the object to radially retract; moving the object to another valve assembly in the well; using the object transition the other valve assembly from a first state to a second state; and performing another stimulation operation in another stage associated with the other valve assembly with the other valve assembly being in the second state.
 20. A method of claim 18, wherein the stimulation operation comprises a hydraulic fracturing operation.
 21. An apparatus usable with a well, comprising: a conveyance cable; and an object adapted to be deployed in the well using the cable, the object comprising: a sensor to sense an environment of the object; a telemetry interface; an actuator; an expandable element; and a control system to: use the sensed environment to determine a location of the object; use the telemetry interface to communicate an indication of the location uphole; use the actuator to selectively expand the expandable element to engage a first valve assembly in response to receiving a first remotely communicated stimulus; use the actuator to retract the expandable element in response to receiving a second remotely communicated stimulus; and use the actuator to expand the expandable element to actuate a second valve assembly in response to receiving a third remotely communicated stimulus.
 22. The apparatus of claim 21, wherein the sensor is adapted to sense at least one of a conductivity, an electromagnetic coupling, a magnetic field and a radioactivity.
 23. The apparatus of claim 21, further comprising: a string comprising a plurality of valve assemblies, each of the valve assemblies being sized to catch an object having substantially the same size; and the cable-conveyed object is adapted to pass through at least one of the valve assemblies and controllably expand to said same size to cause capture of the cable-conveyed tool by one of the valve assemblies. 